Organic peroxyacids have long been known for their excellent bleaching activity. For instance, U.S. Pat. No. 4,642,198 (Humphreys et al) describes a variety of water-insoluble organic peroxyacids intended for suspension in an aqueous, low pH liquid. The preferred peroxy material is 1,12-diperoxydodecanedioic acid (DPDA). Surfactants, both anionic and nonionic, are utilized as suspending agents. When formulated with 10% surfactant, DPDA exhibits good stability under storage conditions. When the surfactant level of the formulation is increased to 22%, a level typical for a heavy-duty laundry detergent, the half-life of the DPDA decreases dramatically. For example, U.S. Pat. No. 4,992,194 (Liberti et al) reports that at 40.degree. C. the half-life of DPDA is only 1 to 2 weeks in a pH 4-4.5 heavy-duty laundry liquid.
EP 0 349 940 (Hoechst A. G.) describes a series of imido peroxyacids, chief among which is N-phthaloylamino peroxycaproic acid (PAP). Suspension of imidoperoxycarboxylic acids in an aqueous system is achieved through use of sodium alkylbenzene sulfonate as reported in EP 0 435 379 (Akzo N. V.). Related technology in EP 0 347 724 (Ausimont) discloses heterocyclic peracids such as N-acyl-piperidine percarboxylic acids. WO 90/14336 (Interox) discloses 6,6'-terephthal-di(amidoperoxy-hexanoic) acid and 6,6'-fumaryl bis (amidoperoxyhexanoic) acid.
Although many of the amido peroxyacids have a quite dramatic bleaching activity, their stability in surfactant solutions remains a considerable problem. These materials also need to be physically stable in terms of thermal and shock sensitivity and in terms of storage stability.
Oxygen-releasing materials have an important limitation in that their activity is extremely temperature dependent. Temperatures in excess of 60.degree. C. are normally required to achieve any bleach effectiveness in an aqueous wash system. The art has partially solved this problem through the use of activators. These activators, also known as bleach precursors or oxidation catalysts react with oxygen releasing materials to generate more effective oxidating species.
A variety of mononuclear manganese complexes used as such oxidation catalysts have been described in EP 458,397 (Favre et al.) and EP 458,398 (Favre et al.). Several dinuclear manganese complexes were first synthesized and described by K. Wieghardt in the "Journal of American Chemical Society, 1988, Vol. 110, No. 22, p. 7398 and in the "Journal of the Chemical Society--Chemical Communications", 1985, p. 1145. The combination of such manganese catalysts with peroxygen compounds is described in Martens et al., U.S. Ser. No. 07/869,587.
It has been surprisingly found that the bleaching activity of organic peroxyacids having a percarboxylic and a carboxylic acid, or a salt functional unit, when combined with manganese catalysts is significantly improved under alkaline conditions.
It is thus an object of the present invention to provide novel peroxycarboxylic acids in combination with manganese catalysts to provide an improved bleaching system and detergent composition containing such system.
It is another object of the present invention to improve the performance of the new peroxycarboxylic acid and manganese catalyst bleaching system in highly alkaline detergent formulations.
A further object of the present invention is to provide a bleaching system which operates over a wide temperature range including those temperatures under 60.degree. C.
Another object of the present invention is to provide bleach improvement through the combination of novel peroxycarboxylic acids and manganese catalysts which are effective in relatively small amounts to provide stable compositions and to avoid substantial incremental cost.
A still further object of the present invention is to provide a method for bleaching stained surfaces such as clothes, household hard surfaces including sinks, toilets and the like, dishware and even dentures.
These and other objects will become apparent in the following description of the invention.